How to Build a Solar Composting Toilet?

Composting toilets have been used for years, and many utilize them in their van, camping, or off-grid home. There are countless avenues to create a composting toilet, with recent advancements in technology raving about solar composting toilets. So, in this guide, we’ll discuss how to build a solar composting toilet.

The primary problem with commercial composting toilets is that some require a tank in or under the house. The units also require urine and feces to be separated, and they don’t keep microbes warm enough to be as efficient as they can be. A solar assisted composting toilet solves those issues and is easier to make than most people realize.

Many people in this lifestyle understand that a solar composting toilet is more efficient than commercial models. Like any other composting toilets, these solar options are adaptable to any living situation since they won’t require a sewer line or septic tank. All you need is the budget, patience, materials, and tools required to make it.

Besides highlighting how to build one, we’ll also discuss what a composting toilet is, what to know about these units, design types, costs, requirements, and uses. We’ll also discuss the benefits of using one, which include environmental reasons, budgeting, versatility, and more.

What is a Composting Toilet?

Many people wonder what a composting toilet is because there’s a general worry about its sanitary and smell. You have to understand that these concerns wouldn’t be genuine if so many people utilized them in homes, boats, RVs, vans, and public places.

The toilets work by using a natural decomposition process free from harmful chemicals. How the units function varies depending on the toilet type. Bacteria break down the waste and turn it into compost. Think of it similar to a compost heap and instead in a closed container with your waste.

The benefits of this method make it clean and safe to use indoors and create the perfect environment for bacteria. It accelerates the process, and the compost manure (also known as humanure) is harmless. Once it’s broken down, you can use the humanure like standard manure.

What is a Solar Composting Toilet?

The issue with commercial composting toilets is the units require a tank inside or under a home, must separate urine and feces, and aren’t as efficient as they could be. Human waste is partially composted because of bacteria in our bodies. When placed in the compost toilet, it becomes a waste full of minerals and nitrogen, making it a valuable fertilizer.

If you have solar already hooked up to your RV, cabin, or home, you can easily transition your composting toilet, which is more efficient than a commercial model. So, a solar composting toilet acts like a standard composting toilet but heats the composter from the run. Keeping the microbes and compost warmer works faster and prevents excess moisture from growing.

How to Build a Solar Composting Toilet

This solar composting toilet is made from four parts. It’s not to be confused with a solar-powered composting toilet since those are commercially bought and come with instructions to install. Instead, this is a solar-assisted composting toilet. The toilet (a 5-gallon sawdust toilet), the tank (made from cement block), the solar cover (made from plywood and safety glass), and an exhaust vent for moisture evaporation (black PVC vent pipe).

With this composting toilet, there’s no need to separate the urine and feces. The feces are collected in the toilet and emptied onto the top of a solar-assisted composting tank that’s outside facing the sun.

The sun will go through the glass and heat it. Doing so will keep the microbes warmer, allowing them to compost quicker than in a non-solar composting toilet. The heat will also help eliminate excess moisture from the waste that escapes from the exhaust pipe.

You can continue using the toilet until the tank is roughly half-full. At that point, you should empty the compost from the bottom of the tank. You can apply the compost to fruit trees and shrubs, or whatever requires humanure.

Remember that a solar-powered composting toilet isn’t designed to handle water from sinks, tubs, showers, or washing machines. It’s meant for human waste composting, and water from other sources is gray water and can be used on gardens, lawns, and trees.

Step One – Build the Toilet

The toilet used with solar-assisted compost can either be a commercial composting toilet or a 5-gallon bucket-style toilet. Sawdust toilets are standard for off-grid homes or mobile settings since you just need to have absorbents handy. The absorbents assist the composting method and reduce the smell.

You can also add toilet paper to these toilets without worrying about messing up the composting process. Use light and thin toilet paper since that’ll be easier to break down. Also, avoid chemicals or cleaners since those will kill the natural microbes essential for this process.

Once you have a commercial composting toilet ordered or have a 5-gallon one built, you can move on to the solar section. You can probably do this method to any composting toilet, though ones close to a private commercial porta-potty work best.

Step Two – Composter Front View

This is a written description of your composter from the front.

Your composter will sit outside, and when it’s complete, it’s emptied through the trap door on top. The top is a plywood box with 2×4 framing and clear plexiglass or safety glass angled at 45 degrees. You can also use old storm windows or shower doors, and the size will vary depending on the tank size.

The tank is best made from cement, which is stacked and grouted, or you can buy a poly tank. As long as the tank is sealed to prevent leaks, it’ll work well. The vent stack is a piece of three-inch PVC attached to the top, and the compost has to sit facing the sun. That way, the sun hits the sunlight and penetrates the glass to warm up the composter.

Step Three – Composter Side View

This is a written description of your composter from the side.

From the side, you can see the compost removal door. The door should be large enough that you can easily use a tool, such as a hoe, to scoop the compost into a bucket or wheelbarrow. Remember to wear gloves when handling the waste and use them for fruit trees and shrubs.

You’ll need to remove compost after it’s half-full, and waste usually takes two weeks to turn into usable fertilizer. Waste at the bottom of the tank will compost faster, so be aware of how you’re scooping the compost. Please don’t rush the process; instead, let the microbes do their thing.

What to Know About Composting Toilets

As great as it is to know how to build a solar composting toilet (or, in this case, a solar-assisted toilet), there’s plenty of information related to composting toilets worth covering. At its core, composting toilets utilize a biological process to break down humans and turn them into humanure.

If you plan on venturing into an off-grid lifestyle, a composting toilet is an imperative portion of that lifestyle. You may find it takes some time to get used to the toilet system, but as long as you’re patient, it’ll become second nature. Let’s discuss design types, costs, requirements, uses, benefits, and a general faq to help you get started.

Design Type

There are a couple types of composting toilets, which include:

Self-Contained Composting Toilet: These toilets are found in RVs, boats, and cabins and are usually portable. People typically fit them in situations where plumbing isn’t possible or complicated such as garages or basements. It’s usually fitted with a vent to eliminate any gases that build. Liquids are usually either separated or drained away, while the solids are kept in a removable container.

Central System Composting Toilet: Also known as a split system, a central system composting toilet is similar to a standard toilet since it hooks up to a septic tank. It needs to remain warm for the composting component to be effective, so these are rarely installed outside.

Besides these design types, there are composting toilet variations worth mentioning. Examples include solar-powered composting toilets, non-electrical composting toilets, electrical composting toilets, worm composting toilets, bucket composting toilets, commercial composting toilets, and more.


How much you spend on a composting toilet depends on the toilet type or if you’re building the toilet yourself. Plenty of people turn a simple five-gallon bucket with a urine diverter into a composting toilet (such as the example above). If you were only to do that, that shouldn’t cost you more than $20 and whatever it costs to keep a stockpile of absorbents.

If you were to take that method and apply the solar-assisted solution we discussed earlier, it wouldn’t cost you more than $150. Some commercial options are thousands of dollars, usually ones that run on electricity and have solar-powered options to the design.

You can spend as little as $20 for a composting toilet or thousands to perfect the matter. Remember that spending a lot of money doesn’t guarantee a high-quality composting toilet. Plenty of expensive composting toilets aren’t great and don’t do their job well.

Requirements and Uses

How much you invest in your composting toilet also depends on the use and point of the toilet. If you live alone and need a portable option for your van and camp, then the $20 five-gallon option will work beautifully. On the contrary, if you have a family in a home but want to limit your environmental impact, you’ll need a higher-quality composting toilet that’ll run you around $1000.

The use point of the toilet comes down to what you need the unit for (i.e., van, house, cabin, outside, etc.). For example, if you need a composting toilet for your van, you’ll need something compact and designed for this lifestyle. On the contrary, if you live in a cabin and need a simple solution for where you live, go with the five-gallon method!

Benefits of Using One

People typically turn to a composting toilet because of how much it lowers their impact on the planet. Flushing away your waste every time you use the bathroom is much more detrimental to the planet than people realize. With water supplies drying up and the planet warmer, you’ll want to reserve as much water as possible.

Besides the environmental benefit, there’s also a massive benefit to the versatility of a composting toilet. You can make a composting toilet work in pretty much any setting without worrying about connecting to a sewer system or septic tank. That way, you can genuinely live off-the-grid as so many people dream about.

  • Saves Money
  • Environment Impact
  • Portable (Depending on the Unit)
  • No Water Requirement (Usually)
  • Reduces Dependence on Traditional Plumbing
  • Fun Project to Start Alone, With Friends, Or With Your Family
  • Reduces Wastewater
  • Creates Compost for Plants

The Smell Myth

There isn’t enough common knowledge about composting toilets because people doubt their performance or have misconceptions about it. Many people think compost toilets for home aren’t ideal because they can cause a foul smell. If you’ve ever used a compost toilet, then you know that’s not true.

Even if there is a smell, the smell is similar to mulch or wood, which isn’t bad. Many high-quality compost toilets eliminate bad smells because they have a fan to put the fumes out. Think of it like an exhaust fan that helps with bad smells and breaks the compost material down.


Are Composting Toilets Illegal?

Regulations for composting toilets depend entirely on where you live. Many states in the United States don’t have regulations for composting toilets, and most people who live in a house with a flush toilet can also use a composting toilet. It’s as long as they have one connected to the sewer or septic system and don’t transport waste across property lines.

It’s vital to check local laws ahead of time to ensure you get the proper permits. Generally, as long as you aren’t harming anyone around you (via their sewer system or causing bad smells), you won’t have any issues. There are also many places where a composting toilet is preferred (RV, van, campsite, etc.).

Is Setting Up Solar-Assited Toilets Hard?

Setting anything up will develop some challenges, especially when it’s more niche, like a solar-assisted toilet. The process is simple enough; the sun hits your compost, so it breaks down faster from the heat. You may run into issues trying to complete that process, but it’ll be worth it once you do.

Where Can I Empty a Composting Toilet?

Humanure is best used for fruit trees or in an outdoor compost pile. Local laws are worth reading online since regulations vary depending on the park and state. For a general rule, you can empty:

  • At a dumping station, which is regarded as the safest place for disposal.
  • On the ground, such as dirt roads in remote spots. Ensure you avoid paved surfaces or places near other campers.
  • Wherever you’d urinate in the wilderness is ideal for dumping urine. Never dump your waste in waterways; urine should always be dumped 200 feet away. Also, avoid storm sewers since the pipes in these dump into rivers and lakes without treatment.

How Does a Solar Composting Toilet Work?

There are two variations of a solar composting toilet. We discussed a solar-assisted composting toilet that uses the sun to hit the compost to help it break down faster. A solar-powered composting toilet uses solar panels to power the toilet, which warms and breaks down the waste from the electricity it generates.

There are plenty of commercial solar-powered composting toilets, but they’re expensive. Though building a solar-assisted composting toilet may take more time, it’s typically more affordable and can operate as efficiently if done correctly.

Where Can I Dump My Urine From My Composting Toilet?

Urine is tricky since it’s not as apparent as humanure, which you dispose of in a dumping station or on a compost pile. Most people dump their urine in an area that’s okay to pee in (somewhere in the wilderness, away from waterways and people). Urine acts as a natural fertilizer for the soil and helps plants grow. I’m sure there are plenty of other uses for urine since urine can be an ingredient in medications, cleaning products, gunpowder, survival uses, textiles, and animal repellent.

Final Thoughts

There’s no better feeling than going across the finish line with a home project, primarily when it benefits the environment as a composting toilet does. Remember, there isn’t a clear-cut way to set up a solar composting toilet. Play around with what we recommend and see if you can do anything to improve it.

Now that you understand how to build a solar composting toilet don’t stop reading about composting toilets. It’s a growing field, and people are constantly coming up with beneficial and helpful information. Please comment below if you have anything worth sharing or want to start a conversation! There’s a lot to discuss with composting toilets, so don’t waste your time getting started!